Exercise bike



FIG. 1 is a perspective view of an exercise bike, showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left view thereof;

FIG. 5 is a right view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is another perspective view thereof.

The broken lines illustrate portions of the exercise bike which form no part of the claimed design. 

The ornamental design for an exercise bike, as shown and described. 